Brodarski Institute

Zagreb, Croatia

Brodarski Institute

Zagreb, Croatia
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The theme of this work is characterization of an ultrasonic low-frequency device, driven at an excitation frequency of around 25 kHz at different electrical excitation levels by using three different methods as proposed in IEC 61847 and IEC 61088 standards. The first method is based on the electromechanical characterization of the device. It consists of measuring the input electrical impedance around the excitation frequency in the unloaded and loaded conditions at a low level excitation voltage of 1 V. The equivalent RLC electrical circuit parameters of an unloaded and loaded device are determined in an anechoic tank and in a vessel at different immersion depths and tip positions in a complex geometry. The electroacoustic efficiency factor of the method is determined by knowing the real part of the radiation resistance and mechanical loss resistance which are transformed into an equivalent RLC electrical circuit of the transducer. The second method consists of measuring the spatial pressure distribution of an ultrasonic device near pressure release boundary in an anechoic tank. The acoustic reciprocity principle is used to determine the derived acoustic power of an equivalent point source in the form of radially oscillating sphere at the excitation frequency. The third method is based on the measurement of power dissipated in a restricted volume of water by using a calorimetric method. Some of the suggested methods are complicated to apply in the high energy ultrasonic devices whose size is much lower than the wavelength in the loading medium due to the occurrence of strong cavitation activity and influence of the sonotrode tip position in the complex standing wave field. However, the measured acoustic power found by using the three suggested methods is compared by means of the electroacoustic efficiency factor defined for each considered method. In the electromechanical characterization, which is made at low electrical excitation levels (applied electrical power of 1 mW at the series resonance frequency), the calculated maximum electroacoustic efficiency factor is around 48% when the influence of standing waves pattern on the radiation resistance is small. It is approximately the same as the one obtained by measuring the derived acoustic power in an anechoic tank (43%) without cavitation activity in front of the tip. When a strong cavitation activity is present in the loading medium, the bubble cloud has a significant influence on the derived acoustic power which is then dispersed in a broad frequency range and the electroacoustic efficiency factor of the method decreases down to 2%. A significant growth of the input electrical impedance magnitude at the excitation frequency is observed when the cavitation activity is present in front of the tip and when it is compared with the impedance magnitude measured at lower excitation levels without cavitation. The power dissipated in the loading medium almost linearly depends on the applied electrical power, with saturation at higher excitation levels. In the linear operating mode the electroacoustic efficiency factor of the calorimetric method (48%) is comparable with the efficiency factors of two other methods. In the nonlinear operating mode, it is larger (71%) due to a significant amount of heat energy released during the cavitation process. © 2010 Elsevier B.V.


Vukadin P.,Brodarski Institute
Proceedings of Meetings on Acoustics | Year: 2016

Underwater noise has been measured and assessed in Croatia from the early seventies of the last century. Brodarski Institute, in that time the technical institute of the ex Yugoslav Navy, has undertaken measurements of various vessel underwater noise as well as underwater ambient noise mainly on two specific locations of interest. Equipment was acquired, techniques and procedures developed and standardized and knowledge and expertise gathered. The measurements and assessment mainly of the vessel underwater noise were continued throughout the eighties. After two decades of virtual standstill, in the wake of requirements for underwater noise monitoring for Descriptor 11 of EU Marine Strategy Framework Directive (MSFD), a series of pilot underwater noise measurements were carried out. The measurement equipment, techniques and procedures as well as the outline of results are presented. The underwater ambient noise monitoring program for the next period has been established and defined and is also presented in the paper. © 2016 Acoustical Society of America.


Elbeih A.,University of Pardubice | Elbeih A.,Military Technical College | Pachman J.,University of Pardubice | Zeman S.,University of Pardubice | And 2 more authors.
Propellants, Explosives, Pyrotechnics | Year: 2013

A series of plastic bonded explosives (PBXs) based on Viton A and Fluorel binders were prepared using four nitramines, namely RDX (1,3,5-trinitro-1,3,5- triazinane), β-HMX (β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX (cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole), and ε-HNIW (ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). The detonation velocities, D, were determined. Detonation parameters were also calculated by means of modified Kamlet & Jacobs method, CHEETAH and EXPLO5 codes. In accordance with our expectations BCHMX based PBXs performed better than RDX based ones. The Urizar coefficient for Fuorel binder was also calculated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kuljaca O.,Brodarski Institute | Horvat K.,Brodarski Institute | Gadewadikar J.,Alcorn State University
MIPRO 2012 - 35th International Convention on Information and Communication Technology, Electronics and Microelectronics - Proceedings | Year: 2012

Paper deals with NN compensated odd symmetric nonlinear actuators. Most actuators are nonlinear sporting odd symmetric nonlinearities such as deadzone and saturation. One of ways of dealing with such actuators is to try to compensate for nonlinearities by static neural networks. Compensated actuators can improve behavior of the system, but then arises the problem of stability analysis because compensated nonlinearity is now complex nonlinearity not described in common literature. One way of dealing with such problem is to perform stability analysis via describing function method. Paper describes the method for compensating nonlinearities, recording describing function and performing stability analysis. © 2012 MIPRO.


Segota S.,Ruder Boskovic Institute | Curkovic L.,University of Zagreb | Ljubas D.,University of Zagreb | Svetlicic V.,Ruder Boskovic Institute | And 2 more authors.
Ceramics International | Year: 2011

The application of heterogeneous photocatalysis is described as an advanced oxidation process (AOP) for the degradation of the diazo reactive dye using immobilized TiO2 as a photocatalyst. Starting TiO2 solutions were prepared with and without the addition of polyethylene glycol (PEG) and TiO2 films were directly deposited on a borosilicate glass substrate using the sol-gel dip-coating method. The surface morphology and the nanoscale roughness of TiO2 films were studied by means of atomic force microscopy (AFM). Structural properties of TiO2 were identified by X-ray diffraction (XRD). The decomposition behaviour of organic compounds from the gels was investigated using thermal gravimetry (TG) and differential scanning calorimetry (DSC). Photocatalytic activities of TiO2 films in the process of degradation of the commercial diazo textile dye Congo red (CR), used as a model pollutant, were monitored by means of UV/vis spectrophotometry. The kinetics of the degradation of the CR dye was described with the Langmuir-Hinshelwood (L-H) kinetic model. The addition of PEG to the TiO2 solution resulted in the changes in the film surface morphology, and affected the ratio of anatase-rutile crystal phases and the photocatalytic activity of TiO2. The TiO2 film prepared with PEG is characterized by higher roughness parameters (Ra, Rmax, Rq, Rz and Zmax), a lower amount of the rutile phase of TiO2, a higher amount of the anatase phase of TiO 2 and a better photocatalytic activity compared to the TiO 2 film without the addition of PEG. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


Fischer D.,Ludwig Maximilians University of Munich | Klapotke T.M.,Ludwig Maximilians University of Munich | Reymann M.,Ludwig Maximilians University of Munich | Schmid P.C.,Ludwig Maximilians University of Munich | And 2 more authors.
Propellants, Explosives, Pyrotechnics | Year: 2014

Sodium 5-cyanotetrazolate sesquihydrate (1) was prepared from sodium azide and two equivalents of sodium cyanide under acidic conditions. Sodium 5-cyanotetrazolate sesquihydrate (1) reacts with hydroxylammonium chloride to form 5-aminohydroximoyl tetrazole (2). 5-Aminohydroximoyl tetrazole (2) is treated with sodium nitrite and hydrochloric acid to form 5-chlorohydroximoyl- tetrazole (3). The chloride azide exchange yields 5-azidohydroximoyl-tetrazole monohydrate (4). When compound 4 is treated with hydrochloric acid, 5-(1H-tetrazolyl)-1-hydroxytetrazole (5) is obtained in good yield. Compound 5 can be deprotonated twice by various bases. Different ionic derivatives such as bis(hydroxylammonium) (6), bis(hydrazinium) (7), bis(guanidinium) (8), bis(aminoguanidinium) (9), bis(ammonium) (10), and diaminouronium (11) 5-(1-oxidotetrazolyl)-tetrazolate were synthesized and characterized. With respect to energetic use salts 6 and 7 are most relevant. Compounds 3-9 and 11 were characterized using low temperature single-crystal X-ray diffraction. All compounds were investigated by NMR and vibrational (IR, Raman) spectroscopy, mass spectrometry and elemental analysis. The thermal properties were determined by differential scanning calorimetry (DSC). The sensitivities towards impact (4: 4 J, 5: 40 J, 6: 12 J, 7: 40 J), friction: (4: 60 N, 5: 240 N, 6: 216 N, 7: 240 N), and electrical discharge (5: 0.40 J, 6: 0.75 J, 7: 0.75 J), were investigated using BAM standards and a small scale electrostatic discharge tester. The detonation parameters of 5-7 were calculated using the EXPLO5.06 code and calculated (CBS-4 M) enthalpy of formation values. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Klapotke T.M.,Ludwig Maximilians University of Munich | Penger A.,Ludwig Maximilians University of Munich | Pfluger C.,Ludwig Maximilians University of Munich | Stierstorfer J.,Ludwig Maximilians University of Munich | Suceska M.,Brodarski Institute
European Journal of Inorganic Chemistry | Year: 2013

There are great demands to develop explosives with higher performance accompanied by reduced sensitivities towards external stimuli, higher thermal stability and improved environmental acceptability. This contribution presents modified nitramines, which were investigated by nucleophilic substitution reactions of potassium salts of 5-amino-3-nitro-1,2,4-triazole, 3,5-dinitro-1,2,4-triazole, 3,5-dinitroimidazole, 2,4-dinitroimidazole, 4-amino-3,5-dinitropyrazole, 3,5-dinitropyrazole, 3,4-dinitropyrazole and 3,4,5-trinitropyrazole on 1,3-dichloro-2-nitrazapropane. The energetic compounds were comprehensively characterized and their detonation parameters were calculated by the EXPLO5 code. Heats of formation were calculated by the atomization method using CBS-4M electronic enthalpies. The presented compounds show detonation performances comparable to pentaerythritol tetranitrate (PETN). In addition, they possess high thermal stabilities and low sensitivities, which make them interesting for further investigations and possible applications as insensitive, high-energy dense materials. The synthesis of advanced open-chain nitramines by nucleophilic substitution reactions with potassium salts of amino and/or nitro substituted 1,2,4-triazoles, imidazoles and pyrazoles on 1,3-dichloronitrazapropane yields neutral energetic materials. The energetic compounds were characterized in detail as secondary explosives. Interesting trends in safety and performance values were explored. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Aas B.,Ludwig Maximilians University of Munich | Kettner M.A.,Ludwig Maximilians University of Munich | Klapotke T.M.,Ludwig Maximilians University of Munich | Suceska M.,Brodarski Institute | Zoller C.,Ludwig Maximilians University of Munich
European Journal of Inorganic Chemistry | Year: 2013

In this work, the syntheses of 2,2,2-trinitroethyl-(2-nitro-2-azapropyl) carbamate (5), its analogue 2-fluoro-2,2-dinitroethyl(2-nitro-2-azapropyl) carbamate (6), and the corresponding 2,2,2-trinitroethyl(2-nitro-2-azapropyl) nitrocarbamate (7) and 2-fluoro-2,2-dinitroethyl(2-nitro-2-azapropyl) nitrocarbamate (8) are presented. The compounds were characterized thoroughly by vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, differential scanning calorimetry measurements and single-crystal X-ray diffraction. In addition, the hitherto unknown low-temperature crystal structures of the starting materials 2-nitro-2-azapropyl chloride (1) and 2-nitro-2-azapropyl isocyanate (2) are presented. Owing to the positive oxygen balance of the carbamate derivatives, their suitability as potential oxidizers in energetic formulations with aluminium as the fuel is investigated and discussed. Standard enthalpies of formation were calculated at the CBS-4M level of theory. With these values and the experimental densities from room-temperature pycnometer measurements, several detonation parameters, such as the detonation pressures and velocities of the crude materials as well as the specific impulses of their formulations with aluminium, were computed by using the EXPLO5 (V6.01) computer program and compared with those of the corresponding mixtures with ammonium perchlorate as the oxidizer. Furthermore, the sensitivities towards impact, friction and electrostatic discharge were determined by using the BAM drop-hammer and friction tester as well as a small-scale electrical discharge device. Two new carbamates and the corresponding nitrocarbamates with 2-nitro-2-azapropyl, 2,2,2-trinitroethyl and 2-fluoro-2,2-dinitroethyl moieties have been synthesized and fully characterized. Owing to their positive oxygen balances, the carbamate derivatives have been evaluated as potential oxidizers in solid rocket propellants and their sensitivities towards mechanical stimuli have been determined. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Klapotke T.M.,Ludwig Maximilians University of Munich | Kurz M.Q.,Ludwig Maximilians University of Munich | Scharf R.,Ludwig Maximilians University of Munich | Schmid P.C.,Ludwig Maximilians University of Munich | And 2 more authors.
ChemPlusChem | Year: 2015

Sodium 5-cyanotetrazolate sesquihydrate (1) is prepared from sodium azide and two equivalents of sodium cyanide under acidic conditions. 1 is then N-oxidized with Oxone to sodium 5-cyanotetrazolate monohydrate (2). Compound 2 is treated with sodium azide and a Lewis acid to form 5-(1H-tetrazolyl)-2-hydroxytetrazole monohydrate (3). Compound 3 can be deprotonated twice by various bases to give ionic derivatives such as the bis(hydroxylammonium) (4), bis(hydrazinium) (6), bis(-guanidinium) (7), bis(aminoguanidinium) (8), bis(ammonium) ( 9), and diaminouronium (11) salt. In addition, compound 3 can only be deprotonated once, as demonstrated by the hydroxylammonium (4) and triaminoguanidinium (10) salts. Compounds 2-5 and 10-11 are structurally characterized by singlecrystal X-ray diffraction. Additionally, compounds 2-11 are characterized by using NMR and vibrational (IR, Raman) spectroscopy as well as mass spectrometry and elemental analysis. Their thermal behaviors are studied from differential thermal analysis measurements, and the sensitivities of the compounds toward shock, friction, and electrostatic discharge are determined. In addition, the heats of formation are calculated (atomization method, CBS-4M enthalpies), and several detonation/propulsion parameters are computed with the EXPLO5 code. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.


Kettner M.A.,Ludwig Maximilians University of Munich | Klapotke T.M.,Ludwig Maximilians University of Munich | Muller T.G.,Ludwig Maximilians University of Munich | Suceska M.,Brodarski Institute
European Journal of Inorganic Chemistry | Year: 2014

This work compares the hitherto unknown crystal structure of N-methylnitramine with its gas-phase diffraction structure. A series of alkaline, alkaline earth and some transition-metal salts were investigated. Furthermore, a series of new nitrogen-rich salts was synthesized and characterized for the first time. The Mannich reaction of N-methylnitramine with formaldehyde yields 2-nitro-2-azapropanol, which was treated with 2-nitro-2-azapropyl isocyanate to furnish new bis-N,O-(2-nitro-2-azapropyl)carbamate. The analogue bis-N,N′-(2-nitro-2-azapropyl)urea derivative is formed when 2-nitro-2-azapropyl isocyanate is treated with water. Owing to the energetic nature of all compounds, their energetic properties were determined. The sensitivities towards impact, friction and electrostatic discharge were determined using the BAM drophammer and friction tester as well as a small-scale electrical discharge device. Standard enthalpies of formation were calculated at the CBS-4M level of theory. With these values and the experimental densities, several detonation parameters such as detonation pressure and velocity of the compounds were computed using the EXPLO5 (V6.01) computer code and compared to currently used explosives. The hitherto unknown crystal structure of N-methylnitramine has been determined. Its Mannich product with formaldehyde was treated with 2-nitro-2-azapropyl isocyanate or water to provide products that were characterized as energetic materials and compared to currently used explosives. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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